Popup error in PO lines based on condition that if PO charge account & Task number are not same

Summary:

Our requirement is to popup error in PO lines based on the condition that if PO charge account and Task number are not same. Here the PO charge account is defaulted with the current DFF setup and category-based accounting. And user can associate project with the Order. Project Task is as good as Natural Account Segment Value. For e.g. 17300, so So we have to do a check on the PO charge code combination (natural account) and match it with the project task. If they are the same, then the user can proceed normally. If they are not same, then